Carburetor



W. STURM CARBURETOR Oct. 25, 1932.

2 Sheets-Sheet 2 Oct. 25, 1932.

l [1A1 all WILHELK STUBM, OF

Patented Oct. 25, 1932' v UNITED STATES PATENT OFFICE STUTTGABT, GERMANY, ASSIGNOB '].0 ROBERT BOSCH AKTIEN- GESELLSCHAFT, OF STUTTGART, GERMANY OABBURETOR Application filed February 18, 1931, Serial No. 515,608, and in Germany February 22, 1980.

The resent invention relates'to carburetors and more particularly to carburetors of the type in which one or more choke tubes are arranged in a mixing pipe and in which the air space of the float chamber is connected to one of said choke tubes and in which the fuel space of the float chamber is also connected to one of said choke tubes whereby the greater vacuum during the air suction stroke of the engine is produced at the mouth of the ipe which is connected to the fuel space of t e float chamber. a In order that suflicient fuel may be supplied to the engine with low speeds of rotation and unfavourable carburation conditions, an auxiliary air channel, having an auxiliary throttle, parallel to the choke tube is arranged whereby the auxiliary throttle automatically opens this auxiliary air channel as soon as the quantity of air required by the motor becomes greater than the quantity which the air choke can admit in the short time available. This condition prevails more particularly when the motor is running at high speed because the size of the choke tubes must be so chosen that a vacuum is produced which is suflicient for supplying the fuel even with low speeds of rotation, i. e. when the air velocities are low.

With high speeds of rotation, more fuel must be sprayed within the unit of time by reason of the greater air velocity in order to obtain the correct mixture. This has already been obtained in a certain degree by various known methods of controlling the gaseous mixture. The quantity of fuel sprayed out however always remains too small in this case for the quantity of fuel taken off cannot exceed that amount which corresponds to the difl'erence in pressure at the mouths of the channels it and f. The difference in pressure cannot be made great however as desired in view of the suction which is necessary to draw fuel into the float chamber. According to the present invention, the auxiliary air throttle which auto matically regulates the air passage lying parallel to the main choke on that account acts on members which reduce the vacuum in the air space of the float chamber when the auxiliary throttle opens and vice versa.

One form of construction of the invention is diagrammatically shown by way of example in the accompanying drawings in which Figure 1 is a section through acarburetor :onstructed according to the present invenion;

Figures 2 to 4 show a detail ofthe auxiliary throttle valves in various positions.

Figures-5 and 6 show a carburetor having an additional air supply to the fuel jet.

Figure 7 is a sectional view of the upper end of mixing tube a showin the relation between the throttle is, the disc p and the passageway 12.

An air throttle b and three choke tubes 0, d, e are disposed in the mixing tube a. The choke tubes 0, d, e have different cross-sections and are arranged in series one behind the other. The air space in a float chamber 9 is connected through a tube 7 to the choke d. A fuel spraying jet h discharges into the smaller choke e.

A throttle is having unbalanced blades tends to keep an air passage i, adjacent the choke a, closed.

A second pipe n, which discharges into the air passage 21 at 0 behind a disc p on the auxiliary throttle is, is connected with the air space of the float chamber. The disc is provided with a conical slot g which is narrowed towards the opening 0 of the pipe n. In the closed position the disc p is adapted to close the outlet of the pipe n while upon opening of the throttle valve the conical slot g uncovers the opening of the pipe n.

The operation of the carburetor of the present invention is as follows At low speeds of rotation all the suction air passes throughthe chokes c, d, e, the throttle k remaining closed. A vacuum which is great enough to draw the fuel from the fuel tank into the float chamber is thereby produced in the choke d. A higher vacuum is produced in the choke e, so that fuel is sprayed out of the jet it. If the quantity of air required by the motor increases, the throttle It opens, so that one part of the air current passes through the passage 71. As soon as the auxiliary throttle it opens the I p. In Figure 3 the throttle is is half opened I air passage 2'.

and the slot 9 is forced a little over the opening 0 so that a. small slot is free for the passage of air into the pipe 12. In Figure 4, the throttle 71: and the opening 0 are shown completely opened.

The air space of the float chamber can be placed in direct communication with the atmosphere in order to reduce the vacuum in the case of high speeds of rotation (not shown). It is however preferable to connect the air space to the mixing tube and more particularly to a place in the auxiliary The cross-sectional area of the channel through which air is fed to the float chamber can also be regulated from the auxiliary throttle by any suitable regulating device for example, by an adjustable cone valve seat and needle valve, slide valves or the like (not shown).

With the carburetor according to the present invention a channel may be provided in the usual manner in the main fuel jet in order to be able, for example, to atomize the fuel more satisfactorily by the introduction of air therethrough or to collect a quantity of fuel which is present in a part of the carburetor when changing over from the idling jet to the main supply jet. The gaseous mixture can be taken up at any suitable place in the interior of the carburetor or from the air space of the float chamber. In Figure 5, the gaseous mixture is removed for example by a channel m from the auxiliary air chamber i at a place in front of the auxiliary throttle is (seen in the direction of the current). This is particularly suitable for motors having low suction pressure with high speeds of rotation. In this case the gaseous mixture and the vacuum can be controlled in ,1

common by the auxiliary throttle is.

In Figure 6 the auxiliary throttle is is provided with a disc 1' having an opening 8. The pipe m opens into that part of the mixlng tube a at which this opening 8 lies when the throttle is is closed. Ifhe connection of the pipe 12 is disposed at some distance from the mouth of the pipe' m so that when the throttle k isopened the pipe at is only gradually freed after the pipe m has been already closed or is almost closed. The quantity of .fuel rayed out is therefore only regulated up to a certain speed of rotation which corresponds to a pre-determined openlng of'the throttle is by a decrease in the supply of gaseous mixture and thence by a reduction of the vacuum in the air space of between the air space of said float chamber and one of said choke tubes, a main air throttle in said mixing pipe, an auxiliary throttle which is in parallel with said choke tubes and is automatically operated by the flow of air through said mixing pipe and means operable by the displacement of the auxiliary throttle to vary the vacuum in the air space of said float chamber.

2. A carburetor comprising in combination a float chamber, a mixing pipe, choke tubes in said pipe, an atomizing jet from the fuel space of said float chamber and dis charging into one of said choke tubes, an air pipe from the air space of said float chamber and discharging into one of said choke tubes, a main air throttle in the mixing pipe, an auxiliary throttle in parallel with said choke tubes and automatically operated by the flow of air through said mixing pipe, a conduit from a position adjacent said auxiliary throttle to the air space of said float chamber and means on said auxiliary throttle for varying the cross sectional area of said conduit to vary the partial vacuum in said air space when said throttle is displaced.

3. A carburetor comprising in combination a float chamber, a mixing pipe, choke tubes in said pipe, an atomizing jet from the fuel space of said float chamber and discharging into one of said choke tubes, an air jet from the air space of said float chamber and discharging in another of said choke tubes, a

main air throttle in said mixing pipe, an

auxiliary throttle in parallel with said choke tubes and automatically operated by the flow of air through said mixing pipe, a conduit from a position adjacent said auxiliary throttle to the air space of said float chamber, a slotted disc on said auxiliary throttle adapted to register to a varying degree with the inlet end of said conduit on displacement of said auxiliary throttle in order to vary the vacuum in the air space of the float chamber.

4. A carburetor comprising in combination a float chamber, a mixing pipe, choke tubes in said pipe, an atomizing .jet in one of said choke tubes and connected to the fuel space of said float chamber, a conduit between any of said choke tubes and theair space of said float chamber, a main air throttle in said mixing pipe, an auxiliary throttle which is in parallel with said choke tubes and is automatically operated by the flow of air throu h said mixing pipe, and means operable b t e displacement of the auxiliary throttle simultaneously to vary the vacuum in the air space of said chamber and the supply of air to the fuel jet.

5. A carburetor comprising in combination a float chamber, a mixing pipe, choke tubes in said pipe, an atomizing et in one of said choke tubes and connected to the fuel space of said float chamber, a conduit between any of said choke tubes and the air space of said float chamber, a main air throttle in said mixing pipe, an auxiliary air throttle which is in parallel with said choke tubes and is automatically operated by the flow ofair through said mixing pipe, a conduit extending from a position adjacent said auxiliary air throttle to the air space of said float chamber, a conduit v extending from a position adjacent said auxiliary air throttle to a point intermediate the endsof said fuel jet and means onsaid auxiliary throttle to vary the cross sectional area of said conduits on displacement of said auxiliary throttle whereby both the vacuum in said air space and the supply of air to the fuel jet is varied.

6 A carburetor comprising in combination a float chamber, a mixing pipe, choke tubes in said pipe, an atomizing et in one of said choke tubes and connected to the fuel space of said float chamber, a conduit between any of said choke tubes and the air space of said float chamber, a main air throttle in said mixing pipe, an auxiliary air throttle which is in parallel with said choke tubes and is auto matically operated by the flow of air through said mixing pipe, a conduit extendin from a position ad] acent said auxiliary air t rottle to the air s ace of said float chamber, a conduit exten' ing from a position adjacent said ing t at the conduit to said air zjsaid auxiliar throttle is gradual y opened after the con .uit from said auxiliary. throttle air throttle to a point intermediate the ends of said fuel pipe, means on said auxiliary throttle to vary the cross sectional area of, I

said conduits on dis lacement of said auxiliary throttle where yboth the vacuum in said air space and the supply of air to the 1 fuel ipe is'v'aried, and means for determinace from to the -fu'el'pipe is substantially closed.

' In testimony whereof I hereunto afiix my signature. a 5 r WILHELM STURM. 

